Position sensor for carpet-tufting machines

ABSTRACT

A carpet-tufting machine position sensor for indicating when the carpet-tufting machine needle bar arrives at or is stopped at a preselected position in its cycle of movement and wherein the needle bar may shake or oscillate thereabout. The position sensor includes a member movable with said needle bar, said movable member having a machine-readable marking; a second reader for reading said marking when the needle bar is in said preselected position; and a first reader for reading the said marking when said needle bar is in a range of its movement other than said preselected position and an adjacent region defined by the maximum displacement of said movable member during maximum parasitic oscillations of the needle bar; and a signal generator connected to the first and second readers for providing a signal only after said second reader has read said marking following an initial reading thereof by said first reader. The indicating transducer thereby provides a single signal when said needle bar initially arrives at said preselected position and ignores subsequent irrelevant arrivals of said needle bar at said preselected position due to uncontrolled oscillations of the needle bar thereabout.

United States Patent [191 Johnson Apr. 2, 1974 Harold L. Johnson, Spartanburg, S.C.

[73] Assignee: Deering Milliken Research Corporation, Spartanburg, S.C.

[22] Filed: Oct. 1, 1971 [21] Appl. No.: 185,734

[75] Inventor:

[52] US. Cl. 112/79 R, 250/233 [51] Int. Cl. D05c 15/10 [58] Field of Search... 112/79 R, 79 A, 266, 219 A;

[56] References Cited UNITED STATES PATENTS 2,268,133 12/1941 Carlson 250/206 3,001,388 9/1961 Maccaffray 66/85 A 3,327,499 6/1967 Schmidt et al. 112/79 R 3,436,655 4/1969 Lundgreen 250/233 Primary Examiner-Jordan Franklin Assistant Examiner-Peter Nerbun Attorney, Agent, or Firm-Norman C. Armitage; H. William Petry; Luke .1. Wilburn, .lr.

I [57] ABSTRACT A carpet-tufting machine position sensor for indicating when the carpet-tufting machine needle bar arrives at or is stopped at a preselected position in its cycle of movement and wherein the needle bar may shake or oscillate thereabout. The position sensor includes a member movable with said needle bar, said movable member having a machine-readable marking; a second reader for reading said marking when the needle bar is in said preselected position; and a first reader for reading the said marking when said needle bar is in a range of its movement other than said preselected position and an adjacent region defined by the maximum displacement of said movable member during maximum parasitic oscillations of the needle bar; and a signal generator connected to the first and second readers for providing a signal only after said second reader has read said marking following an initial reading thereof by said first reader. The indicating transducer thereby provides a single signal when said needle bar initially arrives at said preselected position and ignores subsequent irrelevant arrivals of said needle bar at said preselected position due to uncontrolled oscillations of the needle bar thereabout.

3 Claims, 2 Drawing Figures Q MONO PAIENIEDAPR 21914.

mm; HAROLD L JO WM ATI'OR EY POSITION SENSOR FOR CARPET-TUFIING MACHINES This invention relates to position sensors which are preferably for use in carpet-tufting machines.

There are many applications which require the generation of an electric signal when a mechanical member arrives at a predetermined location. A device which produces such a signal may be termed a position sensor, or a transducer." Such transducers often are used with electronic controls that operate massive machinery. Such transducers may be positioned to sense the arrival of some mechanical member of a machine at a proper location, and then to produce an electric signal which initiates subsequent electrically controlled operations of the machine. An example of such an application is in an electronically controlled carpet-tufting machine, wherein the feed of yarn to the tufting needles for formation of the carpet tufts is initiated at a preselected position in the movement of the needles into and out of a backing material. A typical carpet-tufting machine is massive, and fast-operating, producing, for example, foot wide carpet at a rate of 15 feet-perminute. Such a machine has a 15 foot long needle bar with approximately 1,500 tuft-positioning needles. The bar in each tuft-forming stitch cycle is reciprocally driven into and out of the backing material, while metered lengths of yarn are advanced to the needles at preselected time periods within the stitch cycle to provide yarn tufts in the backing. The backing material moves past the reciprocating needle bar so that the needles insert a plurality of rows of yarn tufts to form the tufted carpet product. Carpet-tufting machines of this kind may be either the traditional looper-type machine, or of the more recently developed type in which the yarns are pneumatically fed through the hollow needles as described in U. S. Pat. No. 3,089,442 to J. T. Short. ln both types of machines the needle bar is very rapidly driven. Electronic controls may be provided for metering various lengths of yarns to the needles in each tufting cycle for the formation of loop height patterned carpets. A control system of this kind, as used in a carpet-tufting machine, is shown and described in Zane Frentress U.S. Pat. application Ser. No. 185,689, filed Oct. 1, 1971, now U.S. Pat. No. 3,74l, l 39 and entitled Control Arrangement for Constant-Rate Yarn-Delivery Carpet-Tuftingv Machines," assigned to the same assignee as the present application. Such high-speed controls are desirable to produce carpet in commercial quantities (e.g., 15 foot wide carpet at 15 feet-per-minute) at a commercially competitive price.

It is desirable, when working with such yarn feed controls, to begin the yarn feed in each cycle at a preselected position of the needle, e.g., as the needles of the needle bar just penetrate the backing material to form the tufts. A position sensor or transducer usually is located on the machine to provide an electric signal to initiate the yarn feeding operation as soon as the needles of the needle bar move into the backing material. Traditional transducers, however, have not functioned properly in all instances because they have given multiple signals which upset the operation of the electronic yarn feed controls and thus, the tuft-forming operation. The cause of such false signaling, I have discovered, and now believe, is due to parasitic oscillation of the needle bar so that it shakes or oscillates when it is stopped or otherwise adversely influenced in its reciprocal movement by external forces. Such shaking typically occurs when the tufting machine is periodically stopped by an operator to repair or adjust a broken or misaligned yarn end, to change backing sheets, to remove the carpet roll, to change yarn, etc. These oscillations disappear quickly and have a characteristic motion often referred to as a damped oscillation. The position sensor of the present invention is coupled mechanically to the needle bar and, when the needle bar first reaches the desired point of initial yarn feed, the sensor produces an electric signal to initiate the electronic controls of the yarn feed mechanism. However, if the tufting machine is stopped or otherwise influenced at the initial point of yarn feed, the needle bar oscillates about its initial yarn feed position before finally settling or stabilizing, thereby causing multiple passes through the initial yarn feed position and multiple electrical signals to be sent to the yarn feed mechanism by the transducer. Thus, each time the needle bar shakes or oscillates at the initial yarn feed position, the transducer sends spurious signals to the controls calling for a new yarn feed cycle. This causes excess yarn to be fed to the needles and produces an irregular tuft height pattern in the carpet product. I

The present invention provides an indicating transducer of a kind which produces a signal when a mechanical member first arrives at a preselected position, and which thereafter ignores parasitic vibrations or oscillations of that member about that position.

Although one aspect of the present invention an indicating transducer for producing an electric signal when a mechanical member arrives at a given location was conceived in connection with carpet-tufting machines, this invention is not limited to such use, but may find a more general application with any such mechanical members which move in a predetermined path and which may shake or oscillate upon stopping at or passing through a preselected position in this path. More generally, the invention may find application wherever it is necessary to indicate the precise instant of arrival of a mechanical member at a given position and at the same time will be independent of parasitic oscillations of such member about such position.

According to one aspect of the invention, there is provided a transducer for indicating when a carpettufting machine needle bar arrives at a preselected position with needles on the bar at a desired position for initial yarn feed, and wherein the needle bar, when it arrives at said preselected position, may oscillate thereabout. Means are provided for mechanically producing a movement of a member dependent upon the position of said needle bar, which member is provided with a machine-readable marking. First means are provided for reading said machine-readable marking when said needle bar is in a position other than said preselected position, and second means provided for reading the marking when the needle bar is in said preselected position, with said first means being located outside the range of displacement of said movable member corresponding to the maximum range of said parasitic oscillations of said needle bar. Signal means are connected to said first and second reading means for providing a signal only after said second reading means has read said marking after said first reading means initially read said marking, whereby said transducer provides a signal when said needle bar initially arrives at said preselected position and ignores subsequent arrivals of said bar at said preselected position due to parasitic oscillations of the needle bar.

According to another aspect of the invention, there is provided a transducer for generating a signal when a mechanical member arrives at a preselected location, and which member tends to oscillate upon initially arriving at said location; and having a machine-readable marking coupled to said member, second means for reading said marking when said member is in its preselected location, first means for reading said machinereadable marking when said member is in a position other than said preselected location or the adjacent region defined by the maximum displacement of said member during said parasitic oscillations, and means connected to said first and second reading means for providing a signal only after said first means has read said marking and upon said second means first reading said marking.

The foregoing and other objects and advantages of the invention will be set forth in, or apparent from, the following description and drawings, wherein:

FIG. 1 is a diagrammatic perspective view of a portion of a carpet-tufting machine and a position sensor of this invention.

FIG. 2 is a schematic diagram of the position sensor of this invention.

Referring now to FIG. 1, there is shown in perspective view a portion of a carpet-tufting machine generally indicated at l, and a position sensor of the invention, generally shown at 2. The carpet-tufting machine includes a needle bar 10, which, in a typical machine, may be feet in length, and on which are mounted a plurality of individual needles 11. Each needle is fed with an individual yarn strand (shown collectively as a yarn sheet 12) from a yarn source above the machine (not shown). A backing material 13 passes beneath the needle bar and during each stitch or tuft forming cycle, the needles are reciprocated into and out of the backing as predetermined lengths of yarns are dispensed by yarn metering devices (shown in block diagram) 14 to form yarn tufts or loops 16 across the width of the backing material. As the needle bar 10 reciprocates into and out of the backing material to form the loops, the backing material 13 is advanced by suitable means, not shown, to form the plurality of rows of yarn loops therein.

Drive means 26 connected to the needle bar 10 includes a motor 24 which rotates a drive shaft 30 carrying an eccentric 28 on which rides a bearing member 32. Bearing member 32 is pivotally connected at 34 to several push rods, one of which 36 is shown mounted for vertical sliding movement in a support bearing 38 carried by the housing unit (not shown). The push rods 36 in turn are connected to the needle bar 10, so that the needle bar reciprocates up and down as the driven shaft 30 is rotated.

At a desired preselected position of movement of the needle bar during each stitch cycle, i.e., each complete revolution of the drive shaft 30 and reciprocation of the needle bar from top position to bottom position and back to top again, the yarn feeding cycle is initiated. Typically in operation of a hollow-needle tufting machine of the type described in afore-mentioned Short U. S. Pat. No. 3,089,442 such initiation might occur just as the needles just penetrate the backing material and yarn feeding continues until the desired amounts of yarn have been dispensed to each of the needles for formation of the yarn loops in that stitch cycle. To initiate such yarn feeding, the position sensor 2 is connected to the drive shaft 30. As soon as it senses the needle bar in the selected position for initiation of yarn feed, it produces an electric signal to begin the yarn feeding cycle to all the needles. A detailed schematic diagram of the sensor or transducer is shown in FIG. 2.

In FIG. 2, the indicating transducer 2 is shown with a mechanical input of the driven shaft 30. Shaft 30 is coupled to a disc 122 having a fine transparent notch 124, extending radially inward from the circumference of the disc 122. The disc 122 is coupled by the rotatable shaft 30 so that it turns 360 every time the needle bar is reciprocated from up to down to up position, or one stitch cycle, by one complete revolution of the shaft 30. As seen, notch 124 is in the position which corresponds to the preselected position of the needle bar for initiation of yarn feed typically just as the needles enter backing 13. As the needle bar is moved by 180 rotation of the shaft 30, the disc 122 also rotates 180, so that the notch 124 is in the uppermost position as seen in FIG. 2. A focused light source 126 is spaced adjacent to the disc and a beam of light 128 falls upon the disc to pass through the notch 124 whenever it passes and the needle bar is in the position for initiation of yarn feed. There is, on the other side of the disc 122, a photo-detector 130, adapted to receive the beam of light when the notch and the needle bar are in the preselected position. Photo-detector 130 produces an electric signal in response to the beam of light, thus indicating that the needle bar has just arrived at the preselected position. This signal is used in an electronic control of the tufting machine to initiate dispensing of yarn. If the reciprocation of the needle bar is stopped or disturbed as it reaches the preselected yarn feed position, it may shake or oscillate slightly. This movement, which is transferred to the disc 122, may be sufficient to move the slit 124 out of the path of the light beam 128, and thereby produce a flickering light to detector 130, which in turn will produce a new electric signal. Each new electric signal gives a false indication that the needle bar has just arrived at the yarn feed position, and that the electronic control mechanism should initiate anew the dispensing of yarn. To avoid these false indications of the controls and oversupply of the yarn to the needles, circuitry is added so that a single electric signal is provided the first time disc 122 moves the slit 124 to its position shown between source 126 and detector 130, and subsequent parasitic oscillations of the disc which interrupt the light beam 128 therebetween are ignored.

A bi-stable multi-vibrator, also called a flip-flop 132 is connected to the photo-detector 130. Flip-flop 132 may be any convenient or conventional type having a pair of input terminals, set S and reset R and set and reset output terminals, Q and Q respectively. When a signal is applied to the set input S, a signal appears and remains on the set output Q. When a signal is applied on the reset input R, the signal is withdrawn from the set output Q and a signal appears on reset output Q. (The reset output 0 of flip-flop 132 is not used.) The photo-detector 130 is connected to a reset terminal R of the flip-flop 132.

Another light source 136 is positioned adjacent the disc 122 at a location of rotation of the disc from the light source 126. Thus, when the disc 122 rotates so that the slit 124 passes the upper position as shown in FIG. 2, a beam of light 138 from the source 136 passes through the slit 124 to a photo-detector 140. Photo-detector 140 is connected to the set S input terminal of the flip-flop 132. Thus, as needle bar moves 180 out of phase from the preselected initial yarn feed position, disc 122 correspondingly rotates 180 and light passes through the slit 124 from source 136 to photo-detector 140. The electrical signal from photodetector 140 is applied to the set input S of flip-flop 132, setting it and producing a signal on its Q output. When the needle bar moves back to the initial yarn feed position, the slit 124 moves so that light beam 128 from source 126 passes through slit 124 to the photodetector 130 to reset flip-flop 132, causing the withdrawal of an output signal from the Q terminal of flipflop 132.

The Q terminal of flip-flop 132 is connected to a mono-stable multi-vibrator 142. This is a circuit which provides an output pulse of a predetermined time duration, e.g., l microsecond, in response to a predetermined input signal, which in the example used here, is a withdrawal of the signal on the Q output of flip-flop 132. For example, if the signal on the output of flip-flop 132 if +5 volts, the mono-stable multi-vibrator 142 is triggered by a negative-going step or change of potential from +5 volts to ground. The output lead from the mono-stable multi-vibrator 142 goes to the yarn feed control mechanism (not shown) to operate the yarn metering devices 14.

Various modifications may be made in the transducer shown in FIG. 2. For example, the light source 136 and photo-detector 140 may be positioned anywhere around the circumference of the disc 122, provided that they not be within the range of displacement of the disc 122 corresponding to the maximum range of the parasitic oscillations of the needle bar.

Thus, there has been shown and described a position sensor providing an electric signal when a mechanical member reaches a given position, and ignoring parasitic oscillations. This instrument originally designed for use with a carpet-tufting machine may find application in other areas of technology.

The above description of the invention is intended to be illustrative and not limiting. Various changes or modifications in the embodiment described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention.

That which is claimed is:

1. A carpet-tufting machine including a reciprocating needle bar, means for moving a backing material past said needle bar for reciprocation of the needles therethrough, means for feeding yarns to said needles at a desired time interval during the reciprocation of the needles to insert yarns into the backing material for the formation of loops therein, a transducer for indicating when said needle bar arrives at a preselected position for initiation of the yarn feed and upon reaching said preselected position may oscillate about said position comprising means for mechanically following the movement of said needle bar, said following means having a machine readable marking, first means for reading said machine readable marking when the needle bar is in a position other than said preselected position, second means for reading said machine readable marking when said needle bar is in said preselected position, said first means being located outside the range of displacement of said following means corresponding to said oscillations of said needle bar, and means connected to said first and second reading means for providing a signal only after said first reading means has read said marking and upon said second reading means initially reading the said marking thereafter, whereby said transducer provides a signal when the needle bar initially arrives at said preselected position and ignores subsequent arrivals of the bar at the preselected position due to needle bar oscillation.

2. A transducer according to claim 1 wherein said machine readable marking is an optically readable marking; said first and second reading means include sources of beams of light, and light detectors, said detectors provide an electrical signal in response to a light beam interacting with said optical marking; and said means for providing a signal including a two state flipflop having one input connected to one reading means and switched to a first state by a signal from said one reading means and a second input connected to the other reading means and switched to the second state by a signal from said other reading means.

3. A transducer according to claim 2 further including mono-stable circuit means connected to the output of said flip-flop for providing a pulse when said flip-flop switches from one state to the other.

00, 71" Dated April 2, 1974 3 Patent No 8 g inventofls) Harold 1.. JQhnS on 5 1'2: is certified that error appears in' the above-identified patent S and that said Letters Patent are hereby correcte as shown below:

Column 4, line 57, delete the second "Q" and insert -Q-.

Column 4, line 61, delete the second "Q" and insert --Q--.

Column 4, line 62, delete "Q" and insert -*Q-.

Column 5, line 25, delete "if" and insert-4s.

Signed ahki sealed this 16th day of September 1974.

{5mm A'tcest':

f MCCOY M GIBSON, JR. C MARSHALL DANN Attesting Officer Commissioner of Patents FGRM PO-H05 fie-69) USCOMM-DC acme-Pee 11.54 GOVERNMENT PRINTING OFFICE 1 \9 59 0-366-334, 

1. A carpet-tufting machine including a reciprocating needle bar, means for moving a backing material past said needle bar for reciprocation of the needles therethrough, means for feeding yarns to said needles at a desired time interval during the reciprocation of the needles to insert yarns into the backing material for the formation of loops therein, a transducer for indicating when said needle bar arrives at a preselected position for initiation of the yarn feed and upon reaching said preselected position may oscillate about said position comprising means for mechanically following the movement of said needle bar, said following means having a machine readable marking, first means for reading said machine readable marking when the needle bar is in a position other than said preselected position, second means for reading said machine readable marking when said needle bar is in said preselected position, said first means being located outside the range of displacement of said following means corresponding to said oscillations of said needle bar, and means connected to said first and second reading means for providing a signal only after said first reading means has read said marking and upon said second reading means initially reading the said marking thereafter, whereby said transducer provides a signal when the needle bar initially arrives at said preseleCted position and ignores subsequent arrivals of the bar at the preselected position due to needle bar oscillation.
 2. A transducer according to claim 1 wherein said machine readable marking is an optically readable marking; said first and second reading means include sources of beams of light, and light detectors, said detectors provide an electrical signal in response to a light beam interacting with said optical marking; and said means for providing a signal including a two state flip-flop having one input connected to one reading means and switched to a first state by a signal from said one reading means and a second input connected to the other reading means and switched to the second state by a signal from said other reading means.
 3. A transducer according to claim 2 further including mono-stable circuit means connected to the output of said flip-flop for providing a pulse when said flip-flop switches from one state to the other. 